Not a fan of the kick, way too click and the guitars don't cover that up at all. Everything sounds very digital (guitars and drums). There isn't much lows or lowmids in this either, but a bass guitar might fix that. (wait..nvm there is one I think? But its only in the sub frequencies, if possible try and get some higher frequencies).
You're not a bad screamer, the intro scream is good but there is too much reverb that wrecks it. You don't want to hear the reverb really, you just want the reverb to make it sound like the vocals are at a bit of a distance, not directly, painfully in your ear. I think your vocals not being seated is coming from them having quite a lot of low-mids and very little low-mids in anything else, but thats a guess. Vocals can be pretty heavily compressed without sounding too bad as long as you set the attack and release right. In a mix I just did I had the threshold at like -36db and with an attack of about 3-5 ms. Not sure about release. Also I really hate the distortion on screams, I think screams sound a lot better without, but if its the only way you can cover up your 'bad' screams (I don't think they're that bad) then I guess keep them.
Gang vocals - I'd do them into a mic one at a time rather than all-at-once (is that what I'm hearing?). You've got the room sound + the massive reverb and they sound like crap. Record a bunch of them and pan them a bit so they're all across L->R and compress them lots, also might want to chuck in some SLIGHT distortion.
I'm hearing a bit of pumping with the cymbals too. They also sound kinda dull, perhaps in comparison to everything else which is really bright.
Sorry if I ripped into it a bit much, but you asked me too ;p
